The field of this invention relates to oil well drilling devices and in particular to an improved rotating blowout preventer.
In oil and gas well drilling, it is typical to mount a rotating blowout preventer on the top of a blowout preventer stack. The rotating blowout preventer generally serves several functions, including the sealing off of the kelly and the diverting of drilling mud into a recirculating mud line. Typically, the mounting of the rotating blowout preventer on the top of a blowout preventer stack locates the rotating blowout preventer just below the rotary table, thus putting it in a difficult position for access for repair. Generally speaking, it is necessary to remove most known rotating blowout preventers entirely from the blowout preventer stack from under the rotary table in order to gain access to the sealing assembly in order to repair or replace the sealing assembly. Removal of the entire rotating blowout preventer from under the rotary table is expensive and time consuming. Generally, it is necessary to replace the seal assembly on a rotating blowout preventer before replacing the bearings, unless the bearings have been contaminated as a result of the leakage through the seal assembly. And, in making repairs to the seal assembly, the possibility of having to replace not only the sealing assembly but also the bearings due to bearing contamination which may occur during repair makes repair of some types of rotating blowout preventers additionally expensive.
The size of a rotating blowout preventer is critical. Most known rotating blowout preventers have an upper, bearing housing which is too large to raise the blowout preventer upwardly through the rotary table for repair.